1. Field of the Invention
The invention generally relates to keyboards used with computer systems and more particularly to a method and apparatus for locking access to the computer through the keyboard until a password is entered.
2. Description of the Related Art
Personal computer systems are becoming more elaborate and are being used for more critical functions. For example, originally personal computers were only used for very simple word processing tasks and spreadsheet applications of relatively limited complexity. Today however, personal computers are being used to form elaborate network systems, both as the work stations and as the file servers and applications of great sensitivity or complexity are being executed. As the complexity of the various applications has gone up dramatically from a simple small spreadsheet application to horribly complex spreadsheets, so has the time required to perform the calculations. In many cases it is convenient for the user to do other tasks and leave his office, leaving the computer unattended. This unattended state is quite common in file server applications of the computer.
Security in the personal computer either locally or on to a network is always of concern. For instance, if an administrator's station is connected into a network, the administrator will have various rights which other users are not allowed. If an ordinary user were to gain access to the network via the administrator's station and begin performing privileged options, disastrous results could occur to the network system. The same is true of access to the file server itself. Alternatively, if a spreadsheet program is in the midst of performing a very long recalculation and the operator wishes to leave for a period of time, another party could come in and see the computer doing apparently nothing and hit a key on the keyboard. This could result in the long recalculation being terminated midstream and having to be restarted. For these reasons it is desireable to be able to lock the keyboard so that access cannot be obtained without some clearance.
In personal computers according to the International Business Machines (IBM) PC/AT class, a physical key switch was used to disable the keyboard activity. If the key switch was in the unlocked position, the keyboard characters were transmitted to the computer system, while when the key switch was in a locked position the characters were not transmitted to the computer system. One advantage of this was that it was very easy to allow keyboard security to be developed in that the key switch merely had to be turned to the locked position, but a disadvantage was that the key switch had to be readily accessible. If for instance the unit was located in a remote location, on the floor or had a very small size so that the key switch had to be located other than on the front of the unit, this need to physically access the key switch became inconvenient. One large advantage of the key switch was that it required no intervention by the processor in the computer system to perform the locking function and thus long tasks could be left running without interference.
When IBM introduced the PS/2 series of personal computers a software based password feature was included. The password value could be loaded into the keyboard interface and activated by software in the computer system so that the keyboard interface did not transfer characters to the system until the password was entered. This was typically done to prevent data entry to the computer system upon initial turn-on, but this feature could be enabled at a later time by means of a utility program. However, because a separate program was needed, this program could not be initiated while other programs had control of the system, such as a spreadsheet program during recalculation. While it was possible to do a hot key scanning sequence using the system processor, a drawback to this technique was that certain operating systems blocked access to the keyboard interface and therefore the password mode could not be initiated.